1. Field of the Invention
The invention relates to a method and a corresponding arrangement for providing an electrical power for an on-board power supply system of a motor vehicle.
2. Description of the Related Art
Electrical energy is becoming increasingly important in a motor vehicle due to its versatility and controllability for implementing new functions. However, a reliable and efficient on-board power supply system is a precondition for using electrical energy in the motor vehicle. More particularly, intelligent energy management is required to ensure that sufficient energy can be made available to the various consumers at any time. Thus, a possible change in load on the on-board power supply system needs to be manageable. This means that the energy needs to be made available in such a way that sufficient energy can be made available to each consumer depending on the importance of the consumer at a given point in time.
An increasing number of electrical loads and a wide spectrum of new safety and comfort functions in a motor vehicle often also necessitate the use of relatively high power energy supplies within the motor vehicle. Functions such as an electromechanical brake, an electrical boost function for a normal internal combustion engine or electromagnetically controlled valves, for example, require loads that often can no longer be supplied sufficiently by a conventional 12 volt on-board power supply system.
U.S. Pat. No. 6,154,381 discloses a system with a plurality of DC-to-DC converters connected in parallel. The system disclosed therein comprises parallel DC-to-DC converters that are controlled by an input control signal interface and an output control signal interface using a smart controller. The disclosed system comprises a smart controller that is based on the fact that the module efficiency varies with the load present, with the result that an optimum operating point exists. However, this requires very complex actuation of the DC-to-DC converters since a synchronized actuation always needs to take place. For this purpose, an additional sensor system and additional wiring is required.
In the context of the present description, a hybrid or electric vehicle with at least two separate electric machines has been considered. Both electric machines are 3-phase synchronous machines, i.e., they are supplied with a 3-phase alternating current. The motor vehicle also has a high-voltage battery that is used for providing direct current. To operate the two electric machines, the direct current made available by the high-voltage battery first needs to be converted into a suitable alternating current, namely the abovementioned 3-phase alternating current. Therefore, in each case one power electronics unit is associated with both electric machines. Each power electronics unit has an inverter to convert the direct current of the high-voltage battery into a respectively suitable alternating current for the respective electric machine.
Against this background of the prior art, the 12 volt on-board power supply system may not be able to supply sufficient power at a specific point in time for all of the rising number of electrical loads and all of the wide spectrum of new safety and comfort functions. Accordingly, an object of the invention is to avoid an associated voltage dip in the event of a short-term overload of the conventional 12 volt on-board power supply system, but instead continuing to provide electrical power.